Apparatus for adjusting fan blades in a turbojet engine

ABSTRACT

Apparatus for adjusting fan blades in a turbojet engine of the type which has a primary duct for conducting air to an engine compressor rotor and a secondary bypass duct with the fan blades extending there-across to form part of an axial flow fan of the engine. The adjusting apparatus is positioned substantially within an annulus arranged between the primary and secondary ducts. The adjusting apparatus includes an annular piston attached to toothed adjusting racks which engage teeth on said fan blades to adjust the fan blade angle of attack upon movement of the annular piston. An arresting or locking mechanism actuable by an auxiliary piston serves to lock the adjusting racks in position. Compressed air supply from the engine to the annular and auxiliary pistons is controlled to prevent actuation of the annular piston while the adjusting racks are locked by the locking mechanism.

United States Patent Pollert Dec. 9, 1975 APPARATUS FOR ADJUSTING FAN3,498,187 3/1970 Stringfellow 92/24 BLADES I A TURBOJET ENGINE 3,720,0603/1973 Pollert 416/157 A [75] Inventor: Wolfgang Pollert,Herbertshausen, FOREIGN A S 0R APPLICATIONS Germany 1,196,588 7/1970United Kingdom 60/226 R 214 726 8/1968 U.S.S.R 416/158 [73] Ass1gnee:Motoren-und Turblnen-Unlon 430557 6 1935 U d d 416 153 Munchen GmbH,Germany mte mg om [22] Filed: Apr. 19, 1973 Primary ExaminerC. J. HusarAssistant ExaminerRobe11 E. Garrett [21] Appl' 353387 Attorney, Agent,or Firm-Craig & Antonelli [44] Published under the Trial VoluntaryProtest lgrgggagnspn January 28, 1975 as document no. 57 ABSTRACTApparatus for adjusting fan blades in a turbojet engine [30] ForeignApplication Priority Data of the type which has a primary duct forconducting air to an engine compressor rotor and a secondary by- Apr.19, 1972 Germany 2218874 p duct with the fan blades extending thereacross to f tf 'alfl f fth '.Thead- 52 US. Cl 60/226 R; 415/130;416/154; 52 g z j g 222 2; g g 'f gg an 51 1m. (:1. F02C 3/06; FOlD 7/0033;;fi gg ggf j jgg f g$32, 23 Fleld 0f Search piston attached totoothed adjusting racks 416/193 415/130 60/226 226 gage teeth on saidfan blades to adjust the fan blade 92/24 27 angle of attack uponmovement of the annular piston. An arresting or locking mechanismactuable by an [56] References C'ted auxiliary piston serves to lock theadjusting racks in UNITED STATES PATENTS position. Compressed air supplyfrom the engine to 1,085,964 2/1914 Briggs 92/27 X the annular andauxiliary pistons is controlled to pre- 2,118,890 5/1938 Maes 92/24 Xvent actuation of the annular piston while the adjust- 2,969,118 1/ 1961Allen 416/154 ing racks are locked by the locking mechanism. 3,251,2785/1966 Royster 92/27 X 3,467,198 9/1969 Ellinger .1 416/157 x 16 Clams,1 Drawing Flgure US. atent Dec. 9 1975 APPARATUS FOR ADJUSTING FANBLADES IN A TURBOJET ENGINE BACKGROUND AND SUMMARY OF THE INVENTION Thisinvention relates to apparatus for changing the blade angle of fanblades in a turbojet engine of ductedfan construction,

In modern turbojet engines of the above-mentioned generic category, thegreater portion of the available engine thrust is normally provided byrelatively largediameter axial-flow fans. The use of these axial-flowfans makes it possible to achieve bypass ratios, relative to the coreengine unit of the respective jet engine, of the order of :1 and over.

One particularly helpful tool in the promotion of engine efficiency hasbeen to adapt the fan to the changed conditions at cruise flight withthe aid of variable-pitch fan blades. It has also been contemplated togenerate reverse thrust by employing negative airfoil angles.

The implementation of such proposed means for varying the pitch of fanrotor blades nevertheless gives considerable trouble from the designpoint of view because the outer row of rotor blades, the angle of whichouter row of blades is intended to vary in an axial-flow fan, isnormally an integral part of the basic engine unit, especially where insuch an arrangement the variablepitch outer fan blades form a jointlyrotating unit with an inner row of rotor blades of a compressor in thebasic engine.

French Pat. No. 2,046,297 proposes to vary the angle of the fan bladesin a turbojet engine of the above-discussed type by means of a complexplanetary gear arranged within a centrally disposed member downstream ofthe hub of the compressor of the basic engine. At least one power shaftextends from said planetary gear and through the primary flow duct ofthis compressor to transfer the actuating movements from the gear to thefan blades via further geared arrangements in the space between theprimary duct and the secondary duct. Apart from the complexity of theparticular arrangement of the actuating gear and the large number ofconnecting drives between adjacent variable fan blades, a furtherdisadvantage of said apparatus is that it will scarcely ensureuniformity and directness of transfer of the torque needed to operatethe fan blades.

The present invention contemplates providing improved apparatus foroperably changing the angle of the fan rotor blades of a turbojet engineof the ductedfan construction such that direct transfer of the actuatingmovement from the drive system to the fan blades is ensured atrelatively little complexity, that uniform .transfer of the actuatingmoment and proper locking of the fan blades in all selected endpositions is possible and that the drive system, as well as theactuating mechanism, will economize space.

It is particularly contemplated by this invention to provide anarrangement where the drive system and the actuating mechanism foradjusting the fan blades are arranged essentially within an annulusintervening between the primary duct and the secondary duct of the jetengine.

The present invention also contemplates a novel arrangement ofcompressed air controlled actuating piston means for adjusting the fanblade angle and compressed air auxiliary piston means for controllingarresting plunger means to lock the fan blades in respective adjustingpositions. The present invention also contemplates a valving and conduitsystem for selectively supplying compressed air from a compressor rotorof the engine to actuate the actuating and auxiliary piston means. Thepresent invention also contemplates an electrical switching means forcontrolling a threeway valve of the valving and conduit system inresponse to the position of the actuating piston means. The compressedair supplying system optimally connects the fixed and rotatable parts ofthe engine so as to minimize space and constructional expenditures whileassuring a reliable control of the respective arresting plunger meansand blade angle adjusting rack means.

These and further objects, features and advantages of the presentinvention will become more obvious from the following description whentaken in connection with the accompanying drawings which show, forpurposes of illustration only, a single embodiment in accordance withthe present invention.

at the longitudinal centerline of a turbojet engine constructed inaccordance with the present invention and illustrates the upper half ofthe forward portion of the engine.

DETAILED DESCRIPTION OF THE DRAWING With reference to the drawing, anaxial fan 1 essentially consists of variable-pitch rotor blades 2 anddownstream of them, fixedly connected guide vanes 3. An outer bypasscasing 4 externally confines secondary or bypass duct 6 by its innerwall 5.

The unitary rotating portion of the axial fan 1 further comprises, readfrom left to right, a central member 8 having a flow-promoting leadingedge contour 7, and a supporting means 9 to carry the variable-pitch fanrotor blades 2 which extends to form an inner wall section 10 of thesecondary duct 6 between the fan rotor blades 2 and the bottom platforms11 of the guide vanes 3. Fixedly connected to the rotating portion ofthe axial fan 1 are further supporting blades 13 which extend throughthe primary duct 12 to form a unitary arrangement, through a centrallydisposed enging hub 16, with an inner shaft 17 of the turbine engine.Arranged in and extending through the primary duct 12 are stay vanes 14dowmstream of supporting blades 13. Hub 16 rotates along with shaft 17,blades 13, central member 8, blades 2, and below described pistonhousing 22 and piston 20.

The stay vanes 14 are followed by further compressor rotor blades 15which connect, through a rotor disk 16', to a further shafting 18 whichenvelops the inner shaft 17.

The rotating unitary portion of the axial fan 1 further comprises andcommunicates with an annular piston 20 which extends coaxially to thelongitudinal centerline 19 of the engine, said piston being arranged foraxially directed sliding motion within a correspondingly arranged,equally cylindrical piston chamber 21. The annular piston 20 is furthersurrounded by a shroud 22 which extends coaxially to the longitudinalcenterline 19of the engine and the lower wall 23 of which serves toguide the annular piston 20.

The shroud 22 further confines a separately sealed cylinder chamber 25formed between it and an upper guide wall 24 for the annular piston 20and that side of the annular piston 20 which opposes the cylinder 3chamber 21.

The annular piston 20 is connected, through an annular support 26, totoothed racks 27 the teeth of which cooperate with the mating teeth onthe necks 28 of the variable-pitch fan rotor blades 2 which aresupported in needle bearings 29, 30. During the actuating movement ofthe fan rotor blades 2, extensions 31 of the racks 27 are carried overrollers 32 which are supported in ball bearings.

As it will become apparent from the drawing all essential elements ofthe actuating system of the fan rotor blades are arranged within theannulus 33 confined by the primary duct 12 on the one hand and thesecondary duct 6 on the other.

Arranged further within this annulus 33, downstream of rotating centralpart 8, is a stationary threeway control valve 34 energized with airfrom the engine compressor in a manner which is not detailed on thedrawing. Inlet lines 35, 36 which extend and are energized commonly orindependently with compressor air from the threeway control valve 34,lead respectively to chambers 37, 38 which in turn communicate, viaducts 39, 40 through the stationary vanes 14, with chambers 41, 42 whichare arranged separately from one another within an air manifoldingsystem 43. From the chambers 41, 42 the compressor air is directed alongthe direction depicted by arrowheads G, H and into annular chambers 46,47 of an auxiliary piston 48 which is arranged adjacent to the shafting17 and extends coaxially to the longitudinal centerline 19 of theengine.

The auxiliary piston 48 is movable towards the lefthand side in responseto a pressure build up in the annular chamber 47. A toothed rack 49 ofthis auxiliary piston 48 cooperates with mating teeth 50 on a bellcrank51. Engagement of a further toothed portion 52 of this bellcrank 51 witha sleeve 53 causes a springloaded plunger 54 to move downward and cleara slot 55 in the toothed rack 27 so that the fan blade 2 is free to moveunder the action of the annular piston 20.

A plurality of such disengageable arresting devices may be provided tosuit any number of supporting blades 13.

It is only when the auxiliary piston 48 has reached the extreme of itslefthand travel and when the respective arresting means of the fanblades 2 have been released that the edge 48 of the piston allowspassage of the compressor air from the annular chamber 47 to a pipe line56. Through this line 56 the compressor air reaches a further annularchamber 57, continues through a hole or cavity 58 incorporated in thesupporting blade 13 and arrives in a chamber 9 which communicates withan air supply line 60. The cylinder chamber 25 is then energized withair from the compressor and the annular piston is moved to its lefthandside to position the fan blade 2.

When the actuating movement of the fan blades 2 is completed, thecontrol pressure from the threeway control valve 34 on the auxiliarypiston 48 is relieved and the auxiliary piston 48 moves to the righthandside (under the force of the spring and the centrifugal force of theplungers) to engage the plungers 54 in further slots 61 in the toothedracks 27 and so arrest the fan blades 2 in their new position.

The air displaced from the cylinder chamber 21 by the annular piston 20during the said movement of the fan blades 2 is allowed to flow, througha line 62, annular chamber 63 and a further hole 64 extending throughthe supporting blade 13, into a chamber 65 of the air manifolding system43, continue through holes 66 to the chamber 46 of the auxiliary piston48 and leave the air manifolding system 43 through the hole or cavity 39in the guide vane 14 in a direction opposite to that indicated by thearrowhead G.

Owing to the described operation and arrangement, the annular piston 20cannot be pressurized with air from the compressor so long as the fanblades 2 are arrested in one or the other end position, e.g.,decelerating or cruise position, by means of the arresting plungers 54.

A further useful aspect of the present invention involves functionallyinterrelating the control of the annular piston 20 with the actuation ofthe threeway control valve 34 so that the auxiliary piston 48 isautomatically restored to secure the fan blades 2 again in position orfor other purposes when a predetermined axial displacement of theannular piston 20 and proportionally therewith a certain stagger angleof the fan blades 2 are reached. For this purpose, iron cores 68 whichproject from the shroud 22, connect to the annular piston 20 andcorotate with the axial-flow fan or engine in operation, are slideablyarranged between oppositely connected secondary windings 69, 70 of adifferential transformer and induce voltages between the secondarywindings that tend to cancel each other out to a degree dependent on theposition of the iron cores 68. Then when the annular piston 20 hasreached a certain end or other position to serve a new stagger angle ofthe fan blades 2, a so-produced voltage drop initiates an electricalsignal causing the threeway control valve 34, through a restoringmember, e.g. to relieve the air pressure on the auxiliary piston 48.

While I have shown and described only a single embodiment in accordancewith the present invention, it is understood that the same is notlimited thereto but also contemplates numerous changes and modificationsas would be known to those skilled in the art given the presentdisclosure of the invention, and I therefore do not wish to be limitedto the details shown and described herein only schematically but intendto cover all such changes and modifications.

I claim:

1. Apparatus for adjusting fan blades in a turbojet engine of ducted-fanconstruction of the type which has primary and secondary ducts; saidapparatus comprising:

drive system and actuating mechanism means positioned substantiallyinside of an annulus arranged between said primary and secondary ductsand including a piston connected to toothed rack means mounted formovement within said annulus, said fan blades including blade teethwhich matingly engage corresponding rack teeth of said toothed rackmeans,

selectively engageable arresting means engageable with said toothed rackmeans to prevent movement of said toothed rack means,

and supporting blade means extending across said primary'duct forsupporting said annulus, wherein said arresting means includesresiliently biased plunger means extending through cavity means in saidsupporting blade means, said plunger means being engageable withrespective spaced slots in said toothed rack means for arresting saidtoothed rack means in positions corresponding to predetermined adjustedpositions of said fan blades.

2. Apparatus according to claim 1, wherein said primary duct is a ductfor supplying air to a compressor rotor of said engine, and wherein saidsecondary duct is a bypass duct with said fan blades forming part of anaxial flow fan of said engine.

3. Apparatus according to claim 2, wherein said engine has alongitudinal engine centerline extending in the direction of air flowthrough said engine, and wherein said secondary duct is arrangedradially outwardly of said primary duct with respect to said enginecenterline.

4. Apparatus according to claim 3, wherein said piston is an annularpiston which is movable coaxially with respect to said engine centerlinein response to pressurized air supplied thereto.

5. Apparatus according to claim 4, wherein said annular piston ismounted within said annulus for movement parallel to said enginecenterline.

6. Apparatus according to claim 5, wherein means are provided fordirecting compressed air from a compressor rotor of said engine as saidpressurized air to move said annular piston.

7. Apparatus according to claim 5, wherein said toothed rack means areconnected to the annular piston through a ring-shaped rack carrier whichextends coaxially to the engine centerline.

8. Apparatus according to claim 7, wherein control means are providedfor controlling the supply of compressed air to said annular piston suchthat supply of .compressed air to said annular piston is prevented untilan auxiliary piston disposed adjacent central shafting of said enginehas first released said arresting means.

9. Apparatus according to claim 8, wherein said auxiliary piston isoperated by compressed air and is movable in a direction parallel tosaid engine centerline.

10. Apparatus according to claim 2, wherein said piston is an annularpiston which is supplied with said compressed air by way of an airmanifolding system adjacent to central shaftin g means of the engine,through ducts in supporting blades extending across said primary duct,and through line means within said annulus to said annular piston.

11. Apparatus according to claim 9, wherein said annular piston issupplied with said compressed air by way of an air manifolding systemadjacent to said central shafting means, through ducts in saidsupporting blade means, and through line means within said annulus tosaid annular piston.

12. Apparatus according to claim 11, further comprising valve meansinterposed downstream of a compressor rotor of said engine forselectively controlling the supply of compressed air from saidcompressor rotor to actuate said annular and auxiliary pistons.

13. Apparatus according to claim 9, further comprising valve meansinterposed downstream of a compressor rotor of said engine forselectively controlling the supply of compressed air from saidcompressor rotor to actuate said annular and auxiliary pistons.

14. Apparatus according to claim 12, further comprising valve controlmeans responsive to the position of said annular piston for controllingsaid valve means.

15. Apparatus according to claim 14, wherein said valve control meansincludes iron core means connected to said annular piston and electricalcoil means adjacent said iron core means, said iron core means and coilmeans being operatively arranged to generate electrical signals forcontrolling the valve means as a result of inductive voltage changesupon changes in position of said annular piston.

16. Apparatus according to claim 15, wherein said valve means is athreeway valve.

1. Apparatus for adjusting fan blades in a turbojet engine of ducted-fanconstruction of the type which has primary and secondary ducts; saidapparatus comprising: drive system and actuating mechanism meanspositioned substantially inside of an annulus arranged between saidprimary and secondary ducts and including a piston connected to toothedrack means mounted for movement within said annulus, said fan bladesincluding blade teeth which matingly engage corresponding rack teeth ofsaid toothed rack means, selectively engageable arresting meansengageable with said toothed rack means to prevent movement of saidtoothed rack means, and supporting blade means extending across saidprimary duct for supporting said annulus, wherein said arresting meansincludes resiliently biased plunger means extending through cavity meansin said supporting blade means, said plunger means being engageable withrespective spaced slots in said toothed rack means for arresting saidtoothed rack means in positions corresponding to predetermined adjustedpositions of said fan blades.
 2. Apparatus according to claim 1, whereinsaid primary duct is a duct for supplying air to a compressor rotor ofsaid engine, and wherein said secondary duct is a bypass duct with saidfan blades forming part of an axial flow fan of said engine. 3.Apparatus according to claim 2, wherein said engine has a longitudinalengine centerline extending in the direction of air flow through saidengine, and wherein said secondary duct is arranged radially outwardlyof said primary duct with respect to said engine centerline. 4.Apparatus according to claim 3, wherein said piston is an annular pistonwhich is movable coaxially with respect to said engine centerline inresponse to pressurized air supplied thereto.
 5. Apparatus according toclaim 4, wherein said annular piston is mounted within said annulus formovement parallel to said engine centerline.
 6. Apparatus according toclaim 5, wherein means are provided for directing compressed air from acomprEssor rotor of said engine as said pressurized air to move saidannular piston.
 7. Apparatus according to claim 5, wherein said toothedrack means are connected to the annular piston through a ring-shapedrack carrier which extends coaxially to the engine centerline. 8.Apparatus according to claim 7, wherein control means are provided forcontrolling the supply of compressed air to said annular piston suchthat supply of compressed air to said annular piston is prevented untilan auxiliary piston disposed adjacent central shafting of said enginehas first released said arresting means.
 9. Apparatus according to claim8, wherein said auxiliary piston is operated by compressed air and ismovable in a direction parallel to said engine centerline.
 10. Apparatusaccording to claim 2, wherein said piston is an annular piston which issupplied with said compressed air by way of an air manifolding systemadjacent to central shafting means of the engine, through ducts insupporting blades extending across said primary duct, and through linemeans within said annulus to said annular piston.
 11. Apparatusaccording to claim 9, wherein said annular piston is supplied with saidcompressed air by way of an air manifolding system adjacent to saidcentral shafting means, through ducts in said supporting blade means,and through line means within said annulus to said annular piston. 12.Apparatus according to claim 11, further comprising valve meansinterposed downstream of a compressor rotor of said engine forselectively controlling the supply of compressed air from saidcompressor rotor to actuate said annular and auxiliary pistons. 13.Apparatus according to claim 9, further comprising valve meansinterposed downstream of a compressor rotor of said engine forselectively controlling the supply of compressed air from saidcompressor rotor to actuate said annular and auxiliary pistons. 14.Apparatus according to claim 12, further comprising valve control meansresponsive to the position of said annular piston for controlling saidvalve means.
 15. Apparatus according to claim 14, wherein said valvecontrol means includes iron core means connected to said annular pistonand electrical coil means adjacent said iron core means, said iron coremeans and coil means being operatively arranged to generate electricalsignals for controlling the valve means as a result of inductive voltagechanges upon changes in position of said annular piston.
 16. Apparatusaccording to claim 15, wherein said valve means is a threeway valve.